A prospective observational study of neonates at UCSF requiring tracheal intubation within 24 hours of birth to quantify the amount of alveolar type I epithelial cell specific antigens in tracheal secretions, and to characterize the changes in these antigen levels over time. These levels and the pattern of change intervals will be correlated to the extent of lung injury assessed clinically and to long term outcome variables such as chronic lung disease. The hypothesis is that the process of lung injury will be marked by increased shedding of type I cells.